Date of Award
Master of Science (MS)
The Conservation Reserve Program supports grassland reconstruction practices that vary in the number (richness) and identity of species added to enrolled sites. Although the program is administered at the federal level, the methods and species pools used to reconstruct these grasslands have changed over time and vary across the United States. Additionally, while the goal is to augment site species pools with desired species, there is some question as to what extent the prescribed practices result in a diverse species pool over the long term given the immense non-native propagule pressure that can exist on these sites. Unfortunately, no large-scale assessments exist of how seeded and observed species change among CRP sites. With this study I assessed program wide patterns in which species are seeded and how this translates to which species occur in a suite of grasslands throughout the Great Plains by comparing species similarity, richness, and turnover. Additionally, I examined the target and nontarget ranges of the top five most frequently seeded species by mapping their seeded and observed locations. Plant surveys were conducted in 109 CRP sites by walking a 50 m × 50 m square in each field and recorded each new plant species encountered within 1 m of transect. The observed dataset was compared with seeding information provided by local NRCS field offices. Through these surveys we recorded 302 species observed in CRP grasslands and through contract seeding information recorded 166 species that were intentionally seeded on the ground. There was no effect of target species richness on non-target species richness. However, observed target species richness increased as target species richness increased. As age increased, richness difference increased between new and old sites, while species richness decreased. Our findings suggest that practitioners select target species based on a longitudinal gradient, which does influence observed species composition among sites. But observed species also had a latitudinal effect on variation in species composition, which is likely caused by local propagule pool presence and target species establishment success. Finally, geographic range varied among seeded and observed range for blackeyed Susan (Rudbeckia hirta L.). I conclude my thesis with a reflection on the more complex parts of the project and reasoning for some of the choices made throughout. From my work it is clear that changes are needed in seeding and management practices to increase seeded species retention and abundance and how local weed species are considered and managed in CRP sites.
Westberg, Lydia M., "Plant Composition And Turnover In Great Plains Conservation Reserve Program Grasslands" (2023). Theses and Dissertations. 5347.